Forest Pathology最新文献

The occurrence of black crust, a disease previously considered secondary, has become a cause for concern due to early leaf fall in rubber trees (Hevea brasiliensis). This study aimed to identify sources of resistance to black crust in 21 clones of rubber trees in a clonal garden. To achieve this, the disease severity was evaluated through eight assessments conducted over a 2-year period. In each evaluation, 15 leaflets from three different parts of the plant (bottom, middle third and crown) were randomly collected, resulting in a total of 45 leaflets per plant. These leaflets were then taken to the laboratory, and the software Leaf Doctor was used to measure the percentage of leaf area exhibiting symptoms of black crust. The results were analysed using the Scott-Knott test at a 5% probability level. The clones with the highest infected leaf area observed during the evaluations were IAC300, IAC418, IAC503, PB311 and RRIM600. Clone IAC511 did not show any symptoms of the disease in any of the evaluations. Clones IAC301, IAC411, IAC501, IAC507 and IRCA111 exhibited low percentages of affected leaf areas. Additionally, this study revealed the progression of the disease over the evaluation period. The infection initially starts on the youngest leaves (crown) in March and subsequently intensifies in the middle third of the plant, corresponding to the youngest leaf previously infected in the crown. Furthermore, environmental data collected in the experimental area over the 2-year evaluation period indicated that the disease manifests with greater severity when the average temperatures fall below 25°C after periods of heavy rainfall, followed by dry periods with low relative humidity. The data presented in this study significantly contribute to the management of this disease in the field by identifying clones where the disease manifests with lower severity.

Tectona grandis is a vital hardwood tree species with substantial industrial and economic importance. From 2020 to 2021, an unusual leaf blight disease was observed in T. grandis saplings planted in the Nursery of the Central Agroforestry Research Institute (CAFRI), Jhansi, India. Disease incidence was recorded as 50%–70% with 40%–82% severity over two consecutive years on over 1000 saplings. The leaf blight disease was extensive, leading to defoliation of young leaves and mortality of teak saplings in the nursery. The pathogen was identified as Alternaria alternata following standard laboratory procedures and sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal RNA (rRNA). The pathogenicity of two isolates, A. alternata TgAa1 and TgAa2, was proven under greenhouse conditions. Phylogenetic analysis revealed the close association of TgAa1 and TgAa2 with other pathogenic A. alternata strains in the NCBI database. A. alternata is considered a severe foliar pathogen, known to cause leaf spot and leaf blight diseases in many annual and perennial plant species. Correct diagnosis and prevention are emphasized to contain the spread of teak leaf blight to other regions in India. This is the first report of A. alternata causing Tectona grandis leaf blight in the Bundelkhand region of India.

Teratosphaeria nubilosa is the predominant causal agent of Teratosphaeria leaf disease (TLD) in experimental plantations of E. globulus in Brazil. It exhibits slow vegetative growth and lack of sporulation in in vitro culture, making it difficult to obtain enough ascospores for mass inoculation. This study aimed to establish an inoculation method based on ascospore ejection from naturally infected leaves and use it to assess the response to T. nubilosa of eucalypt species and interspecific hybrids. First, the optimal temperature and incubation time for ascospores ejection from naturally infected E. globulus leaves were determined in vitro. Then, these optimal conditions were used to assess the response of eight eucalypt genotypes to T. nubilosa inoculation using ejected ascospores. The infected leaves were placed above (T1), above and under (T2) or under (T3) the plants to be inoculated. Significant differences in disease incidence, disease severity and plant defoliation were observed among genotypes and inoculation treatments. Plants exhibited higher incidence, more severe symptoms and more defoliation when exposed to T2. E. globulus and E. globulus × E. nitens clones were the most susceptible whereas an E. benthamii clone was immune. The sources of resistance identified in this work can be used in hybridization programmes with E. globulus to obtain interspecific hybrids expressing resistance to T. nubilosa and retaining the desirable traits for planting in temperate climates. The inoculation method optimized in this work could be used for small and medium-scale screening of Eucalyptus spp. resistant to TLD. However, periodic validation of the species and genotype of the fungus associated with the naturally infected leaves used for inoculation and confirmation of the resistant phenotype of the selected eucalypt clones or progenies through experimental replications over time must be conducted.

Dieback of dwarf pine scrub (Pinus mugo subsp. mugo) shoots can limit the growth of this species in subalpine areas of the Carpathian Mountains. In July 2023, extensive shoot decline was observed in P. mugo patches in the West Tatra Mountains in southern Poland. Symptomatic shoots showed shoot tip dieback and red-brown needle discoloration. Internal symptoms included dark discoloration of the pith parenchyma and necrotic lesions in shoot periderms. In this study, we described the symptoms of P. mugo shoot dieback and surveyed the culturable fungi from asymptomatic and symptomatic P. mugo shoots, as well as the bases of needles growing from shoots. In addition, we conducted phylogenetic analyses to distinguish between potential cryptic species of Sydowia polyspora. The dwarf pine scrub shoots and needles were sampled from four patches in the Polish Tatra Mountains. In total, 128 distinct taxa were identified. Ascomycota was dominant, representing 96.6% of the isolates. Among the taxa identified, Sydowia polyspora crypt. sp. I, Lachnellula calyciformis, Mollisia sp. 8, Tympanis sp., Epicoccum mezzettii, E. nigrum, Infundichalara sp., Lophium mytilinum, Cytospora sp., Soosiella sp., Cladosporium westerdijkiae and Hendersonia pinicola were most frequently isolated. In most cases, tissue type and sample site significantly affected the abundance and composition of colonizing fungi. Only S. polyspora was found consistently in all sample types, suggesting that this fungus may be responsible for the shoot dieback of P. mugo. Phylogenetic analyses demonstrated that S. polyspora should be treated as a species complex containing at least four cryptic species (referred to as groups I–IV), that are highly host-specific to different conifer species. We also found several other well-known pathogens, namely Allantophomopsis pseudotsugae, Botrytis cinerea, Cytospora sp., Fusarium sp., Sirococcus conigenus and Tympanis sp., which may cause considerable damage to Pinus spp. shoots. Among them, only Cytospora sp., and Tympanis sp. were found often. This is the first comprehensive survey of the fungi associated with extensive shoot dieback of P. mugo in the Carpathian Mountains, and this research led to the discovery of numerous new fungal species associated with P. mugo.

In September 2022, hazelnut trees in six orchards in the Çarşamba district of Samsun province, a major hazelnut production area in the Black Sea region of Türkiye, showed symptoms of leaf yellowing, shoot dieback, decline, basal stem rot and the presence of brown bracket-like sessile basidiocarps. Approximately 5%–10% of hazelnut trees were affected, highlighting the significant impact of the disease. A comprehensive morphological analysis was conducted to characterize fungal isolates obtained from symptomatic tissues as G. adspersum. This analysis incorporated features observed in basidiomata from declining trees and those reproduced after isolates were cultivated on wheat grain for spawn production and grown on an oak sawdust-based substrate. Confirmation of identification was achieved through the utilization of the internal transcribed spacer (ITS), large subunit (LSU) and small subunit (SSU) loci, along with sequencing and subsequent phylogenetic analysis. The G. adspersum isolates generally exhibited no significant growth differences at similar temperatures but demonstrated enhanced growth at 30°C, while growth was completely inhibited at 40°C. Incompatible reactions between isolates confirmed that distinct genotypes were present, highlighting genetic diversity within the species. In the pathogenicity trials, employing a single infested wheat grain per inoculation at the wounded site, hazelnut suckers exhibited distinct brown discolouration surrounding the inoculation site following a 2.5-month incubation period. Significantly, lesions exceeding 3 cm in length were observed, providing clear evidence of vigorous pathogenic activity by G. adspersum. This study is the first report of G. adspersum causing butt rot in hazelnuts, underscoring the significance of this finding for hazelnut cultivation and providing a foundation for future research and disease management strategies.

Plants of the genus Myrciaria are commonly cultivated in the northern region of Brazil for fruit production. Symptoms of leaf spot in camu-camu (Myrciaria dubia) trees are frequently observed. The objective of this study was to identify the etiological agent associated with anthracnose in camu-camu using the concept of morphological and phylogenetic analyses. Leaves with symptoms of anthracnose were collected from camu-camu plants in the state of Roraima, Brazil. Morphological identification; sequencing analysis of CAL, GAPDH, CHS-1 and TUB2 gene regions; a pathogenicity test and reisolation of the fungus from symptomatic artificially inoculated plants confirmed C. theobromicola as the causal agent of the disease. This is the first record of C. theobromicola causing anthracnose in camu-camu in Brazil.

Bursaphelenchus mucronatus Mamiya & Enda, 1979 is a wood nematode widely distributed over Palearctic coniferous forests. It has two subspecies, that is, B. mucronatus mucronatus and B. mucronatus kolymensis, which present molecularly different East Asian and European genotypes, respectively. The European subspecies is found mainly in Europe and Siberia, while the East Asian subspecies occupies mostly Eastern regions of Asia. However, local isolates of both subspecies have been occasionally reported from various localities in Europe and Asia. Our field isolation and molecular (DNA ITS-RFLP) identification of 21 recently collected populations of B. mucronatus revealed only 4 isolates representing clearly East Asian or European genotypes, while the remaining 17 isolates showed intermediate genotypes with electrophoretic band characters of both the above types. Further individual crossbreeding, in vitro, of nematodes representing European, East Asian, and intermediate genotypes provided experimental evidence for the process of intraspecific hybridization between both subspecies, spontaneously taking place in the forest. Such a widening of the B. mucronatus genetic variation may have its effect on a range of reported in the literature direct interactions between this native, nonpathogenic nematode species and the genetically similar, causative agent of the pine wilt disease B. xylophilus which can colonize the same host trees, use the same insect vectors, compete, and crossbreed inter-specifically.

Leaf chlorosis and root browning with root rot were observed on mature Cinnamomum camphora (Linn) Presl between 2021 and 2023 in Hangzhou, Zhejiang province, China. Three strains of fungi consistently isolated from the diseased roots were selected for identification and pathogenicity test. They were identified as Fusarium decemcellulare Brick based on the morphology and phylogenetic analysis using combined sequence data. The pathogenicity of the strains was verified by inoculating on C. camphora seedings in pots. Fusarium decemcellulare was reisolated from the artificially inoculated roots of C. camphora seedings. To our knowledge, this is the first report that F. decemcellulare causes root rot on C. camphora worldwide and its potential threat should be monitored.

The chestnut gall wasp (CGW) Dryocosmus kuriphilus is a serious pest of chestnuts (Castanea sativa) in many chestnut growing areas in Turkey. Out of 200 galls randomly collected from four different areas of Yalova and Giresun provinces, 116 showed necrosis, while 84 were asymptomatic. Fungi associated with the necrotic and asymptomatic galls were determined based on morphology and DNA sequencing. Gnomoniopsis smithogilvyi, Colletotrichum acutatum, Penicillium glabrum, Botrysphaeria dothidea, Trichoderma atroviridea, and Botrytis cinerea were found on 49, 11, 10, 8, 7, and 1 necrotic galls, respectively. On the other hand, G. smithogilvyi, Fusarium proliferatum, Aureobasidium sp., C. godetiae, Rhizopus stolonifer, P. glabrum, C. acutatum, Cladosporium sp., Alternaria spp., and Aspergillus sp. were hosted by 37, 35, 15, 14, 12, 8, 6, 3, 1, and 1 asymptomatic galls, respectively. Seven fungi, G. smithogilvyi, C. acutatum, F. proliferatum, B. dothidea, Cryphonectria parasitica, Diplodina castanea, and Penicillium sp. were isolated from 31, 6, 4, 1, 1, 1, and 1 of the dead larvae of D. kuriphilus, respectively. Two fungi, F. proliferatum and Penicillium sp., were isolated from the adults of Torymus sinensis, a parasitoid of CGW. Pathogenicity of G. smithogilvyi, C. acutatum, and F. proliferatum detected from dead larvae of D. kuriphilus and galls was tested on young chestnut saplings: the former two produced necrosis while the third one did not.

Wood-decay fungi are major contributors to damage wood and logs, resulting in substantial economic losses. This study assessed the decay caused by Trametes flavida and Daldinia eschscholtzii on Gmelina arborea, Samanea saman, Albizia lebbeck, Acacia auriculiformis and Swietenia mahagoni. Both fungi demonstrated their ability to decay wood. However, the extent of damage varied significantly among the tested hardwood species. Findings showed that Trametes flavida caused greater wood mass and density loss than Daldinia eschscholtzii. Among the tested hardwood species, G. arborea was found to be more susceptible to the decay fungi, followed by S. saman, A. lebbeck, A. auriculiformis and S. mahagoni, respectively. The study will encourage the scientific management of timber and logs in sawmill depots to minimize the decay of wood and incurred economic loss.